This invention relates generally to a method for controlling well blow outs, especially when those wells are located in a body of water and the well cannot be conventionally controlled using drilling mud.
The environmental hazards, as well as the hazards to personnel, of well blow outs have become increasingly important, especially where those blow outs have taken place in ecologically sensitive areas, such as the coast of California or off the Yucatan Peninsula of Mexico. As a result, the prior art is replete with disclosures of methods for controlling such blow outs. However, none of these methods is of universal application, and each poses some economic or technological drawback.
U.S. Pat. Nos. 4,116,285 and 4,185,703 disclose methods and apparatus for producing deep boreholes in which the borehole is filled at least partially with a substance which remains in the liquid state and has a density greater than the mean density of the ground strata being drilled. Thus, any infiltrations from the formation into the borehole, as well as drilling debris, naturally move upward to the free surface of the liquid substance filling the borehole. Various filling substances which are disclosed include antimony trichloride and other antimony, selenium and tellurium compounds, as well as silica gel, cryolite and metals having a low melting point. It is indicated in these patents that, as temperatures increase with increasing depth of borehole, solid pieces of metallic selenium and tellurium (which eventually melt near the bottom of the borehole) may be used as a substitute for or in conjunction with the more volatile liquid antimony and selenium compounds, which are used at the lower temperatures associated with holes up to about 4,500 meters in depth. In any case, the upward migration of debris and infiltrations into the borehole may be accelerated by circulating the liquid filling the borehole with a pump.
U.S. Pat. No. 3,647,000 discloses a method for capping the uncontrolled flow of oil and gas from petroleum wells located in a body of water by a procedure performed below the level of the water's surface in a location which is free from wave action and safe from the danger of fire or explosion. The method involves the tapping of a window or access opening into the well casing or tubing through which the well fluids are flowing below the surface of the well, crimping the casing or tubing above the point of the tap and injecting solid plugging bodies which lodge within the constriction in the production tubing string and form a plug blocking the flow. Heavy non-combustible mud is then pumped into the production tubing through the tapped-in access line until the weight of the injected mud overcomes the formation pressure, thus terminating well flow. Neither the nature of the plugging bodies nor the nature of the heavy mud is specified.
U.S. Pat. No. 3,926,256 discloses a method for preventing blow outs in offshore wells by providing the well with an apparatus in which pins extend into the passage through which oil or gas are flowing, the uncontrolled flow being stopped by the injection into the pin-containing region of a sealer material such as balls of rubber or fiber, natural or synthetic, Fiberglas, aluminum, shredded Teflon, and the like, followed by a mastic which acts as the sealing agent.
U.S. Pat. No. 4,133,383 discloses a method for terminating formation fluid blow outs by introducing into the formation a low viscosity fluid which has the property of becoming highly viscous under the influence of heat. Gelling and sealing agents, including hydratable polysaccharides that are cross-linkable under heat and pressure, are disclosed. The stability of the polysaccharides at temperatures above 300.degree. F. is protected by the provision of an encapsulated base in the aqueous fluid through which the polysaccharides are introduced into the formation, the encapsulated base being released at about 300.degree. F., thereby offsetting the degrading effect of the acids generated in the formation at that temperature.
It is also known to apply dry ice or liquid nitrogen to the exterior of the string through which the well is blowing out and thereby freeze the blowing fluids to form a plug in the string.
In another development, the casing string through which the Ixtox I well in the Gulf of Mexico was blowing out during the summer of 1979 was treated with some success in an effort to cut down the flow by pumping in iron and lead balls.